Plasma Treating Mixed Metal Oxides to Improve Oxidative Performance via Defect Generation

The generation of structural defects in metal oxide catalysts offers a potential pathway to improve performance. Herein, we investigated the effect of thermal hydrogenation and low-temperature plasma treatments on mixed SiO₂/TiO₂ materials. Hydrogenation at 500 °C resulted in the reduction of the material to produce Ti³⁺ in the bulk TiO₂. In contrast, low temperature plasma treatment for 10 or 20 min generated surface Ti³⁺ species via the removal of oxygen on both the neat and hydrogenated material. Assessing the photocatalytic activity of the materials demonstrated a 40-130% increase in the rate of formic acid oxidation after plasma treatment. A strong relationship between the Ti³⁺ content and catalyst activity was established, although a change in the Si-Ti interaction after plasma treating of the neat SiO₂/TiO₂ material was found to limit performance, and suggests that performance is not determined solely by the presence of Ti³⁺.